1 Muhr Non-Conventional PD-Measurements (07004-01)

Non Non –– Conventional PD Conventional PD –– MeasurementsMeasurements

IEC TC42 WG14IEC TC42 WG14

Michael MuhrMichael Muhr

Institute of High Voltage EngineeringInstitute of High Voltage Engineeringand System Management and System Management

University of Technology GrazUniversity of Technology Graz

M. Muhr

IEC TC42 WG14

PD – location and detection

Important diagnostic tool as nondestructive test

Quality assurance for insulation systems

MacroscopicMacroscopic--physical effects by partial dischargesphysical effects by partial discharges

• High frequency wave• Heat• Chemical reaction• Pressure wave, sound• Light• Dielectric losses

PD PD –– MeasurementsMeasurements

M. Muhr

IEC TC42 WG14

PD PD –– MeasurementsMeasurementsDetection methods

- Conventional electrical measurement• Integration at frequency domain

Narrow-bandWide-band

• Integration at time domain

- Electrical measurements with high frequencies• HF / VHF method – 40 MHz to 300 MHz• UHF method – 300 MHz to 3 GHz

- Acoustic measurements – 10 kHz to 300 kHz

- Optical measurements – ultraviolet – visible – infrared range

- Chemical measurement

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Sensors)Measurements (Sensors)

Acoustic

piezoelectric transducer

Electric

electromagnetic wave-guideOptical

modulation-interferometerLDIC T. Strehl

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (GIS Measurements (GIS –– PD PD –– Decoupling)Decoupling)

Spacer

external sensorultra wide band

inductive coupler

external sensoracoustic coupler

internal sensorcapacitive (window-) sensor

external sensorwindow sensor

standard couplingcapacitance

LDIC T. Strehl

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (UHF)Measurements (UHF)UHF – Partial Discharge Detection

• Transient electromagnetic waves (TEM, TE and TM modes)generated by partial discharges

• Frequency range 300 MHz to 3 GHz

• Measuring techniqueNarrow band-bandwidth appr. 5 MHzWide band-frequency range 300 MHz to 1,5 GHz

• In 420 kV plants – upper critical frequency 1 GHz

• In 123 kV plants – upper critical frequency 1,5 GHz

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (UHF)Measurements (UHF)

• Sensors

- Conventional UHF sensors• Disc sensor• Cone sensor

- Mobile UHF-window sensor

- Field grading electrodes

M. Muhr

IEC TC42 WG14


Externally mounted barrier and window sensors for GIS

M. Muhr

IEC TC42 WG14

sealing ring

plug

cone sensor

GIS - flange

insulatingmaterial

connecting lead

cover plate

sealing ring

plug

cone sensor

GIS - flange

insulatingmaterial

connecting lead

cover plate


Sectional view and mounting of an UHF PD disk sensor

Sectional view and mounting of an UHF PD cone sensor

disc sensor

GIS - flange

insulatingmaterial

connecting lead

cover plate

sealing ring

plug

disc sensor

GIS - flange

insulatingmaterial

connecting lead

cover plate

sealing ring

plug

M. Muhr

IEC TC42 WG14


- Damping dependent by

• Frequency

• Geometrie

• Conductor material

• Mode type- 1-2 dB / km (TEM, TE)- 4 dB / km (TM)

• Reflection and refraction

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (UHF)Measurements (UHF)- Sensivity

• Measurement equipment• Failure location• Location of the sensor• Facility configuration

Frequency response of the window-mounted sensor compared with a UHF coupler for GIS. The shaded region defines the specified operating band of 500 to 1500 MHz

M. Muhr

IEC TC42 WG14


Spectrum of a loose particle measured with a window sensora) Without flange extensionb) With flange extension of 10 cm

M. Muhr

IEC TC42 WG14


Sensitivity of developed UHF sensors

M. Muhr

IEC TC42 WG14


• CalibrationSensitivity verification

- Comparison conventional measurement-UHF measurementPulse generator

- Demands of rise time and duration can be done

• Field of application- GIS, GIL- Transformer monitoring

M. Muhr

IEC TC42 WG14


Decoupling unit with bushing tap adapter

PO

WE

R T

RA

NS

FOR

ME

Rbu

shin

g ta

p

MO

NIT

OR

ING

SY

STE

M

LDIC T. Strehl

M. Muhr

IEC TC42 WG14


GIS

XLPE-CablePD reception zone

Band pass filter 300-800 MHz, Ampl., Attn. and UHF/VHF Converter

PD Decoupling Loop

UHF-Sensor PD Acquisition

LDIC T. Strehl

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (HF / VHF)Measurements (HF / VHF)HF / VHF – Partial Discharge Detection

• PD's in polymeric insulations shows a duration of several nanoseconds. Transformation in frequency domain.Frequency spectrum up to 100 MHz

• Measurements techniqueFrequency range 40 MHz to 300 MHz

- Narrow-band, band width < 2 MHz- Wide-band, band width > 50 MHz

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (HF / VHF)Measurements (HF / VHF)

• Sensors

- Capacitive

- Inductive

- Electromagnetic

Used PD sensors

M. Muhr

IEC TC42 WG14


Schematic representation of a Rogowski coil to the inductive PD detection and the equivalent network as well as example of use (inside a joint)

• Rogowski-coilFrequency range 1-40 MHz

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (HF / VHF)Measurements (HF / VHF)• Directional coupler

Frequency range 2-500 MHz

• Film electrodes- Capacitive sensor- Frequency range 1-50 MHz- Sensitivity 1 pC to 10 pC

• Yoke-coil- Inductive sensor- Frequency range 2-50 MHz- Sensitivity 10 pC

Principle of the coupler sensor

M. Muhr

IEC TC42 WG14


• Damping- Geometric proportions- Discontinuities- Impulse form

• Calibration- By means of two sensors with equal behaviour

• Application- High voltage cables- Transformers

M. Muhr

IEC TC42 WG14


PD-Localisation with Field-SensorsLDIC T. Strehl

BA

C-Sensor

LDP-5

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Acoustic)Measurements (Acoustic)

• Acoustic Partial Discharge Detection- Acoustic signal as a result of the pressure build-up caused by the

generated spark in the insulation- Frequency spectrum 10 Hz up to 300 kHz- Different wave types (longitudinal and transversal waves) with

different propagation velocities

• Measurement Technique- Microphones and ultrasonic directional microphones- Sound sensors, accelerometers and piezo-electric converters

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Acoustic)Measurements (Acoustic)• Sensors

- Piezo-electric (sound emission)- Structure-born sound-resonance- Accelerometer- Condenser microphones- Opto-acoustic sensor

Ultrasonic measuring instrument with

directional microphone

PD acoustic sensor

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Acoustic)Measurements (Acoustic)• Damping

- Equipment dispersion- Construction- Insulation structures- Point of origin- Gas pressure- Encapsulation material- Absorption during a

medium to another- Geometrical spreading

of the wave

• Sensitivity

Example: Sensitivity of the acoustic PD detection in 300 kV GIS

M. Muhr

IEC TC42 WG14


IEH S. Tenbohlen

M. Muhr

IEC TC42 WG14


• Calibration- Normally not possible- Function control with a wide-band acoustic pulse

• Field of application- High voltage cables- GIS- Transformers- Overhead lines

M. Muhr

IEC TC42 WG14


IEH S. Tenbohlen

A disc-shaped UHF-sensor for a standardized valve (DN 80) was installed in serviceTransient recorder with 3 GHz analoge bandwidthNo amplification of the UHF-signals

380/220 kV, 200 MVA single-phase transformer

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Chemical)Measurements (Chemical)Chemical Partial Discharge Detection

- Determination of decomposition products in the insulating material caused by pd's

- Oil analysis – generating of gases

- Air pd's – NOX, ozone

- Sensors and analyzers

- Calibration – not possible, chemical analysis

- Field of application

• Gas analysis• DGA• Ozone• H2

• Rotating machines• Gas-insulated switchgears• Transformer diagnosis

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Chemical)Measurements (Chemical)

Fehlerart 42

22

HCHC

2

4

HCH

62

42

HCHC

PD - <0,1 <0,2 D1 >1 0,1 – 0,5 >1 D2 0,6 – 2,5 0,1 – 1 >2 T1 - >1 <1 T2 <0,1 >1 1 – 4 T3 <0,2 >1 > 4

• T1 temperatures T < 300° C• PD partial discharges

• T3 temperatures T > 700° C• D2 discharges with high energy

• T2 temperatures 300° C < T < 700° C• D1 discharges with low energy

IEC DGA Gas ratio values

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Optical)Measurements (Optical)Optical Partial Discharge Detection

• Based upon the detection of light produced during the discharge

• Measurement technique- Ultraviolet- Visible- Infrared- Surface detection- Detection inside of the equipment

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Optical)Measurements (Optical)

• Sensors- UV-corona- Night vision- Low-light enhancer- Photodiode,

photomultiplier (withfibre optic cable)

Wellenlänge nm

400 700 1000 1300 1600re

lativ

e E

mpf

indl

ichk

eit

1,00

0,75

0,50

0,25

0,00

Wellenlänge nm

400 700 1000 1300 1600re

lativ

e E

mpf

indl

ichk

eit

1,00

0,75

0,50

0,25

0,00

Relative spectral sensitivity as a function of the wavelength of different detector materials

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Optical)Measurements (Optical)• Damping

• Sensitivity- Dependent from the equipment configuration, location of the

defect, location of the sensor, cable connection, measuring instrument

• Calibration- Not calibratable

• Field of application- Localisation of detective regions

- Geometry- Medium- Absorption, dispersion, refraction- Scattered light- Operational equipment

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (Optical)Measurements (Optical)Modulation Interferometer for direct PD Signal Field Sensing:• Light passes through a medium with an electric field applied across the material, the

light will experience a phase shift• Applied Inorganic LiNbO3 Mach-Zehnder Interferometer (Organic Polymer Films

under development)• Bandwidth: 1 Hz – 10 GHz• DFB Laser drives Single Mode Optical Fiber

Transmittance:

T(V) = cos2 ( )Ф0

2π2

VVπ

Application: directly fitted above semicon layer (joint, cable) or in GIS tube

Laser

Sample V

I1

I2LDIC T. Strehl

M. Muhr

IEC TC42 WG14


amplifierFilter

opt. receiver

Voltage supply

PC

lens

Fluor. opt. fibre

conv. opt. fibre Oszi

shielding

≈≠Net

optical signal linking

Signal transmission Signal processing, analog

Signal collection processingand evaluation

Plate

Lens

Peak

fluor. fibre

Peak

Plate

M. Muhr

IEC TC42 WG14


conventional detected PD-Signal optical detected PD-Signal

Comparison conventional (band limited) and optical detected PD signal

1000 ns

M. Muhr

IEC TC42 WG14

PD PD –– Measurements (System Setup)Measurements (System Setup)

LDIC T. Strehl

PD Monitor

Sensitivity check

Sensor A Sensor B

400 kV Cable

OpticalReceiver

Polarisation-tuner

Laser Source1550 nm20 mW

Amplifier LowPass

HighPass

Calibrator

Termination

MZ Modulator

Termination

M. Muhr

IEC TC42 WG14

method frequency sensor*) sensitivity calibration

UHF 0,3 GHz – 3 GHz

0,5 – 1,5 GHz

0,05 pC **)

< 1 pC in the laboratory

4 - 5 pC

no***)

sensitivity verification

HF / VHF 20 MHz – 300 MHz

0,5 – 80 MHz

1 pC


10 pC on-site no***)

acoustic 10 Hz – 300 kHz

(1 MHz)

30 – 120 kHz

< 1 pC **)


5 pC on-site

no***)

sensitivity verification

optical 200 – 1100 nm

(wave length)

200 – 850 nm

0,5 pC **)


3 pC on-site no***)

chemical - - yes/no - decision no

*) Application example

**) Measuring sensitivity if charges pulses are directly injected

***) during model arrangements in the laboratory a calibration with the conventional electrical measurement is possible.

PD PD –– MeasurementsMeasurements

M. Muhr

IEC TC42 WG14

IEC IEC ProposalProposal

"Non-conventional PD-measurements"In the past few years, there has been the development of many so-called non-conventional PD measurement methods. Partial discharges (PD’s) generate pressure waves, sound, light and electromagnetic waves. These physical effects can be detected by different sensors and so there is the possibility to detect PD’s with non-conventional methods besides the conventional electrical measurement. The main method for PD measurement is electromagnetic (HF/VHF/UHF) and acoustic measurements. Also, there have been a lot of papers published using these methods. Therefore, IEC TC42 has in the meeting of September 1st, 2005 in Beijing, decided to proceed with this new work item called “Measurement of PD’s by electromagnetic (e.g. UHF) and acoustic methods” and to form a new working group for this task. As convener of this new WG, Prof. M. Muhr, Austria, has been proposed and voted and also six countries have agreed to provide a team member. The task of this new WG is to collect all the used applications of these methods to compare them with each other and to look at their frequency range. Another differentiation of the measuring technique is if it is a narrow bandwidth or a wide band frequency measurement technique. This work will also include the use and the techniques of the different sensors, their frequency range and their sensitivity. Also, it will investigate the issue of the methods, the possibility of PD location and if a calibration or in minimum a sensitivity check is possible. The WG will start with the electromagnetic methods and after finishing will move forward to the acoustic methods.

M. Muhr

IEC TC42 WG14

IEC Purpose and JustificationIEC Purpose and Justification

a) The specific aims and reason for the standardization activity, with particular emphasis on the aspects of standardization to be covered, the problems it is expected to solve or the difficulties it is intended to overcome.

b) The main interests that might benefit from or be affected by the activity, such as industry, consumers, trade, governments, distributors.

c) Feasibility of the activity: Are there factors that could hinder the successful establishment or general application of the standard?

d) Timeliness of the standard to be produced: Is the technology reasonably stabilized? If not, how much time is likely to be available before advances in technology may render the proposed standard outdated? Is the proposed standard required as a basis for the future development of the technology in question?

e) Urgency of the activity, considering the needs of the market (industry, consumers, trade, governments etc.) as well as other fields or organizations. Indicate target date and, when a series of standards is proposed, suggest priorities.

f) The benefits to be gained by the implementation of the proposed standard; alternatively, the loss or disadvantage(s) if no standard is established within a reasonable time. Data such as product volume of value of trade should be included and quantified.

g) If the standardization activity is, or is likely to be, the subject of regulations or to require the harmonization of existing regulations, this should be indicated.

M. Muhr

IEC TC42 WG14

"Non "Non –– Conventional PD Conventional PD –– Measurements"Measurements"Extraction of Generic Terms 1Extraction of Generic Terms 1

• Description of EM PD phenomena- PD occurrence in discharging defects- Frequency/time behaviour- Specifics of HV components- Applicability for detection

• Sensoring- Types, parameters, positioning

• Transmission aspects- Relation between EM behaviour of the HV component, sensor

characteristic in the EM field and the measuring system characteristics- Definition of suitable reading parameters

• System check(s)- Sensor sensitivity- Performance check- Sensitivity check

M. Muhr

IEC TC42 WG14


• Standardization:- Definition between PD [pC] and Correlating quantity - Requirements of the Instruments- System check

• Problems to be solved- Quantity of EM - PD Source e.g. E [Volt/meter]- Quantity of Sensor / Antenna e.g. [meter / square meter / gain]- Quantity of Instrument Reading e.g. [m Volt / m Watt_dBm / p Joule]- Definition of correlating Quantity between PD [pC] and Instrument Reading

/ Conditions: definable transfer function (a +b x^2 + c x^3 + …..) / (n + m y^2 + o y^3 ……) and low standard deviation

• No Standardization - Applicable sensors- Test and measuring Configurations- Interpretation – Task of the Component Panels

M. Muhr

IEC TC42 WG14


EM – PD SourceBasic Quantity E [Volt / meter]

Sensor – AntennaBasic Quantity e.g.

[meter]

ReadingQuantity

[Volt]

PD [pC]Quantity [m Watt]

Low Standard DeviationDefinition of Transfer Characteristic

Definition of TransferCharacteristic

Low Standard Deviation

System Check

Physical Generic Aspect

MathematicalTerm

Quantity [Volt]PD [pC]High Standard Deviation

M. Muhr

IEC TC42 WG14

Thank you for attentionThank you for attention

1 Muhr Non-Conventional PD-Measurements (07004-01)

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